Various optical systems are required to operate in adverse environments, in which solid particles and/or fluid droplets and/or other agglomerations of one or more materials of various stickiness or viscosity (herein collectively termed “debris”) may adhere to the lens and reduce image quality.
A particularly difficult environment to view is the inside of the human body. Various medical instruments have been devised for this purpose. Endoscopes and laparoscopes are devices used for observation, diagnosis, and treatment, e.g. biopsy or cauterization inside a human or animal body. They comprise an objective lens system, normally at the distal end and means for carrying the images gathered to the proximal end of the device where they can be directly viewed or displayed allowing the operator to observe the space in front of the objective lens. The objective lens can be part of a camera, an optical relay system, or can focus the image onto a fiber optic cable that transfers the image to the viewer. Commonly an endoscope lens becomes at least partially occluded by body fluids and particles. In many cases the occlusion becomes so great that the endoscope becomes inoperative. In such circumstance the lens must cleaned. One method of cleaning the lens is to spray the outer surface of the lens with a jet of water, air or other gas. The water or gas is supplied to one or more nozzles on the distal end adjacent the lens through channels that are an integral part of the endoscope assembly. In some instances the endoscope must be withdrawn from the body for cleaning and reinserted—a time-consuming, risk-increasing and often uncomfortable procedure.
Another solution to this problem is a centrifugal lens protector. A centrifugal lens protector comprises a spinning glass disc that is placed in front of the lens, so that the debris is intercepted by the disc. The centrifugal force generated by the disc as it rotates throws the debris towards the circumference of the disc, where it falls off or sometimes accumulates but in any case no longer interferes with the image.
U.S. Pat. No. 5,223,880 to Rapp describes a camera protector in which the disc is integrated with a rotor of a magnetic motor, with a casing surrounding the disc being the motor housing.
U.S. Pat. No. 5,315,333 to Nash provides a single motor coupled to the disc using a band. The disc is mounted on two lines of bearings. The lens protection device is mounted on the camera, to isolate lens from gyroscopic and vibration forces.
Australian application 9515074 describes another band-based system, in which the disc is said to rotate at between 2600 and 3000 RPM. It is suggested to use a curved or hydrophobic surface to assist in water removal. The motor can be powered using the camera battery pack or using a separate battery.
U.S. Pat. No. 7,104,657 by the inventor of the present invention, the description of which, including publications referenced therein, is incorporated herein by reference provides a lens protector for medical viewing devices. The lens protector is comprised of a rotating window and a motor that causes the rotation. Both of these components are enclosed by a casing located at the distal tip of an endoscopic device in front of the objective lens of the viewing system. The casing, motor, and rotating window are supplied as a unit that can be attached in various ways described in the patent to any existing endoscopic device. In practice, it has been discovered that the use of the invention does indeed solve the problem of the accumulation of body fluids and particles in front of the lens but nevertheless the picture quality is sometimes degraded.
Any endoscopic device that is equipped to provide visualization of the treatment region within a body cavity comprises illumination means, e.g. optical fibers or LEDs, located next to the objective lens, in order to illuminate the area of interest. Because the rotating window of the lens protector in U.S. Pat. No. 7,104,657 also covers the illumination means, some of the light emitted from the endoscope is partially reflected from the inside of the window onto the lens. This back reflected light is the cause of the image quality degradation mentioned above.
It is therefore a purpose of the present invention to provide endoscopic devices that are equipped with rotating lens protectors for the objective lens of the visualization means, wherein back reflection of light from the illumination source is prevented.
Further purposes and advantages of this invention will appear as the description proceeds.